docs: def _build_meta(meta: str, pipelines: Iterable['Pipeline']) -> 'Pipeline':
          """Build a pipeline with a given meta-argument.
  
          :param meta: either union or intersection
          :param pipelines:
          """
          return Pipeline(protocol=[
              {
                  'meta': meta,
                  'pipelines': [
                      pipeline.protocol
                      for pipeline in pipelines
                  ]
              },
          ])